3.3.3. Carcinogenic Metal Risk Assessment. The URs for
the two known carcinogens (Cr and Ni) and two probable
human carcinogens (Cd and Pb) were defined in a previous
study22 and presented in Table 5. According to the mean
concentrations of each carcinogenic metal in PM2.5 collected in
different sampling points, we could calculate the lifetime cancer
risk. From Table 5, it can be seen that the trend was the risks in
the mechanical workshop > the risks in the manual dismantling
workshop > the risks in the southeast. Any cancer risk less than
the threshold value (10−6
) is considered negligible by the U.S.
EPA. From the results, we could see that the lifetime cancer risk
of Cr exceeded the threshold obviously and it may have a
cancer risk on the workers and residents